Tuesday, August 20, 2013

What does an adjustment do?

Adjustment is the conglomerate term Chiropractors use to describe a set of modalities (treatment tools).  They vary enormously from so called 'low-force' techniques to the traditional HVLA adjustment (High Velocity Low Amplitude (short distance)).  In the hands of a clinician who is trained and experienced at knowing not just what but when and how to apply it these approaches can be very effective for various neuromusculoskeletal disorders.

Sometimes people will ask "what does it do".

Here's a list of some effects which have been observed during neuroscience research (courtesy of Matthew Long CDI)

  • Engages mechanoreceptors to open mechanically gated ion channels and initiate a current flow into the largest and fastest primary afferent neurons.
  • Uses a rapid lengthening of muscle to activate the dynamic components of the muscle spindle receptor to fire 1A afferents at a high frequency in order to modulate central neurology (greater than 200 Hz).  
  • Alters the gain on the muscle spindle system to change muscle tone via the action of gamma motor neurons that innervate the intrafusal muscle fibres.
  • Produces a ‘novel’ blend of sensory input that alters the state of the dorsal horn and shapes the responsiveness of spinal cord neurons to future inputs.
  • Induces plastic changes in neural circuits via long-term potentiation and depression, depending upon the type of circuit i.e. manipulation can produce long-term depression of the projection neurons of the pain pathways.
  • Alters the genetic responses in spinal cord neurons and those in the higher centres.
  • Produces a propagated response in neurons in the ipsilateral cerebellum.
  • Alters the frequency of firing of lower motor neurons to produce a change in muscle tone, joint stability, position and motion.

Doug Scown

PAIN is reliable in an unreliable way

The guys at The University of South Australia have put a great deal of work into the study of chronic pain.

Acute pain (as we might experience when we step on a nail or twist an ankle) is straight forward.  Do this - get that.  But what about pain which persists?  And what about pain which comes and goes or changes it's nature and location?  Confused?  Welcome to the world of chronic pain and the way it colours injury and dysfunction.

Health professionals still overwhelmingly deal with pain as if it were acute and something was damaged or broken.  Patients who present with continuing pain are told that their nerves are still healing or perhaps they have re injured the injury.  Is this accurate?

Chiropractors tend to see people with chronic or long term complaints.  Their problem often began yrs before but in the early stages their pain and dysfunction was brief and self limiting.  Furthermore it was aggravated by specific things, usually an awkward movement such as lifting and twisting.  Recently though the patient reports that their pain came from "nowhere".  "I slept wrong", "It just went out and now it's not going away".  In short their brief, self limiting problem has become chronic, 'unstable' and aggravated by trivial movements.  Additionally the pain has changed. It was sharper and "here".  Now it's sometimes sharp, often a dull ache or burning and it's spreading.  It feels like it could just "go" on me.

The patient has developed chronic pain.  The brain learns and changes through repetition and the repetition of pain can do interesting things with a plastic or moldable neurology.  Pain itself is a complex experience suffice to say it's important to pin down what originally triggered the problem (the disc, joint, bone, distortion - the diagnosis) and what may have led to it weakening (usually a combination of injury, sensation disturbance, lifestyle and of course genetics/epigenetics).

Ref   Apkarian et al. (2004) Chronic back pain

Do backs 'go out'

Can your back 'go out'?

The old model for SPINE (which is still used a great deal) was 'bone out of place'.  It made sense.  Hard bone, soft nerve, ouch.  Then someone applies a force to a joint, it may feel better and (particularly if we hear a pop) we connect the dots.

"My bone was out, it hurts, it's pinched a nerve, I heard it pop back in, now it feels better = bone out of place."  It feels like this, it sounds plausible and to cap it off even health practitioners (and specialists) still believe this to be true.  And if they don't they are not sure how else to explain it.

The trouble with this theory was this - there was never any evidence for it.  Short of fracture and dislocation there is NO evidence that we can put a displaced joint 'back in'.

So what on earth is happening? 

The model is now multifaceted and the research supports that MOST changes are due to neurophysiological changes (changes in the nervous system when physical modalities are applied (exercise, joint manipulation, etc) .  A big one is normal proprioception or 'joint position sense' which can be disrupted by injury, lack of use and pain.  Even if we ignore all of the other effects this deficit in the brains ability to properly sense and therefore control and protect the spine is reduced.

Physically based treatments aim to 'leverage' or target these deficits thus improving this innate body function.

The following research from the Physiotherapy profession illustrates the failure of the 'bone out of place' model to explain the effects we see.